The invention relates to apparatus for use in processing molten plastics, particularly but not exclusively for use in extruding plastics strands in the production of plastics granulate.
Plants for the production of plastics granulate comprise a polymerisation vessel and a pump disposed downstream thereof and adapted to deliver the molten plastics into a die head from whose die bores plastics strands are discharged downwardly. The strands are then taken up by a haul-off and cooling device in which the plastics strands become hardened whereupon they are granulated. The process which takes place in the polymerisation vessl normally requires several hours during which the product polymerises while being constantly stirred. The plastics granulate is therefore produced in batches. During the entire period it is necessary not only for the polymerisation vessel to be heated but for all parts of the plant between the polymerisation vessel and the die head to be heated in order to avoid solidification in such parts of the apparatus of the plastics derived from the last processed batch, an effect which would render the plant useless. It is therefore not possible to avoid temperature-sensitive plastics becoming thermally damaged in the hot pipe lines and ports between the polymerisation vessel and the die head during the polymerisation process. Operation with known plants therefore made it necessary to discard the batch of granulate which was initially produced.